Human evolution is the evolutionary process that led to the emergence of Homo sapiens as a distinct species of the hominid family.
Dryopithecus, Ramapithecus, Australopithecines, Homo habilis, Homo erectus, Homo sapiens neanderthalensis are the ancestors of modern man (Homo sapiens) in chronological order.
Ramapithecus was a man-like primate which lived about 14-15 million years ago.
Australopithecines lived about 2 million years ago. They had characters of both ape and man.
Homo habilis was the first human-like being which existed about 2 million years ago.
Homo erectus existed about 1.5 million years ago.
The order of human evolution is
Hence, Ramapithecus is the most primitive ancestor of Homo sapiens from the given options.